While the anime is very faithful to the visual novels, some changes in the progression of the cases were made due to time constraints, and others to better suit the story's pacing. This results in some gags (Sahwit hilariously throwing his toupee at Phoenix's face) and optional content (the ladder/stepladder debate) being cut out, and changes in locales (Cody's interrogation taking place during the investigation).
Though not every change was completely positive. The stun gun scene in "Turnabout Goodbyes" isn't nearly as impactful and memorable in the anime as it was in the game, now that it's only between Maya and a random officer, instead of von Karma himself knocking out both Phoenix and Maya.
A notable example of this trope application giving positive impact to the adaptation is "Turnabout Big Top." The witnesses' gimmicks were toned down and several scenes were altered or added in order to give them more character depth; Moe had more serious moments, Max Galactica negotiated with the ringleader to increase other troupe members' salary to motivate them to do better, Regina got to show her reaction when Phoenix revealed that the reason ringleader died was to take the fall for her and then directly apologized to Acro when he was taken away which results in her realization more personal, and some others.
Another less popular change was the decision to change Adrian Andrews and Celeste Inpax from mentor/protégé to sisters in the anime. While it's often assumed that the change was to snuff out the Homoerotic Subtext between the two, it may have been a pragmatic choice; in the game, a lot of time is spent verbally explaining Adrian's complex emotional problems and dependent personalty that lead her to idolize Celeste, mimic her behaviour and subsequently attempt suicide when she died. Replacing all this with "they were sisters" explains her motives in one sentence with no other explanation required.
Area 88: The anime adaptations of the manga leave out the quirky humor that occasionally showed up in the manga. It also wisely chose to leave out the quasi-Science Fiction elements that seemed to belong more in G.I. Joe than a serious contemporary war melodrama. In the manga, the anti-government forces employed devices such as land-based aircraft carriers, robot-controlled F-18 fighters, a drill missile, laser sentries, and a massive air fortress. There was also an inexplicable connection between the Asran Civil War, The Mafia, Yamato Airlines, Communists, and various other groups, including a Nebulous Evil Organization. The manga also included the successful use of nuclear weapons on several occasions, something that would have made worldwide headlines in the real world but, amazingly, went totally unnoticed by the public in the manga. The anime adaptations remove all of the byzantine subplots, conspiracies, eccentric guest characters, and soap opera twists. In the original manga, unlike the OVA, Kanzaki's arrest is hardly the end of him. Like any villain worth his salt, he always has an escape plan and keeps coming back with another grandiose scheme. The anime's focus is on Shin's perceived loss of his humanity. Also, it should be noted that the manga series, which lasted seven years (1979-1986), inexplicably lasted more than twice as long as Shin's forced mercenary contract of three years. It was still running when the original OVA was produced. The OVA's ending had to be different from the manga as it wasn't finished yet. The U.S. manga adaptation lasted briefly (42 issues and then briefly in Animerica magazine) and was nowhere close to the end, but by the time of the brief Animerica run, the series had already declined due to the meandering subplots. What little is known (to non-Japanese speaking readers) about the manga's ending is that fans feel it was a cop-out. In the final battle, Shin gets his revenge on Kanzaki, but gets shot down, gets amnesia and forgets all about his experiences at Area 88. He and Ryoko get married and live happily ever after. The OVA's strong and powerful ending is widely considered preferable.
Following the fall of Wall Maria, the story of the manga skips the training arc, only to cover it some volumes later. The anime series doesn't, following the events' chronological order instead. Also, as the anime reached the end of the first season, there was an increase in Filler scenes (approved by the mangaka and mostly well-received by the fanbase) to pace the show so the season could end at a certain dramatic point. These scenes also expand on many side characters.
In order for season 2 of the anime to be 12 episodes and not less, the mangaka approved the addition of two extra flashback scenes: One based on a single panel from the manga, and one that didn't appear in the manga until two arcs later. Even though the latter scene prematurely hinted at several story revelations, it was met with praise due to manga fans getting to see a recent chapter adapted early for a change.
The first cour of season 3 covered the Uprising arc, which mangaka Hajima Isayama had many regrets about. Several scenes were switched around and condensed to allow for a better and faster pace, with the first action-filled encounter with Kenny the Ripper being placed at the end of episode 1, when in the manga it takes place 7 chapters into the arc. All of these changes were approved and suggested by Isayama himself.
The 1997 anime of Berserk certainly toned down much of the series's violence, but is perhaps more well known for emphasizing themes of friendship and ambition — and not in an optimistic way — more than the manga did. This was a compromise with Berserk's long supernatural plotline. Most of the series is actually a flashback. The anime also did away with all the slapstick and face faults, which created a more consistently bleak mood. The changes are usually accepted by fans, seeing as creator Kentarō Miura gave his approval.
Bokurano, since the director of the anime didn't like how the story got way too dark for his taste. Quite a few things got changed as a result.
A few of the pilots' orders got switched around. For example, Kako is third in the anime, meaning that he's the first to pilot after learning that the chosen pilots die even if they win, making his reaction somewhat more fitting. By contrast, in the manga, Chizu notes that the pilots are gradually getting used to what is happening.
When Komo fights, instead of baiting the enemy pilot with a piano recital, she has a more standard battle with an enemy mech, which she wins easily.
Near the end, instead of Kana having a turn and dying like everyone else, in the anime, Dung Beetle tries to manipulate Kana into contracting, but Jun and Youko manage to turn the tables on him and kill him, leaving Kana as the Sole Survivor.
In the anime adaptation of Brave10, because of time constraints some characters disappear and others take their roles, some fights and events are cut and some villains are weakened.
The Bunny Drop anime ends one year into Daikichi's stint as surrogate father to Rin, and doesn't for a moment acknowledge the developments of the manga's second half. Many who checked out the manga to see how the story continues there ended up wishing they hadn't.
While the anime version of Boys over Flowers closely follows the original manga, the live action show compressed the story into a neat two-season package. There are instances of both characters (Kazuya and Makiko's roles are now given to Sakurako, making her much more devious) and events (important events from three separate parties now all occur at one party) being combined, and there are several storylines where someone tries to seduce Tsukasa or Tsukushi which are done away with entirely.
The Dangers in My Heart: The manga consists of usually 11-page main chapters, some of early on are standalone and end on gags, along with a lot of short extra chapters. The anime adaptation changes or omits certain details and switches the timeframe of events so that each chapter can flow into the next within episodes, and merges a select few of the extra chapters in. For example, two separate scenes of Nanjou talking to Yamada and Chii in Chapters 21 are merged together.
In DearS, the producers quickly realized that they wouldn't be able to juggle the full cast of characters and the sci-fi plot in a 12-Episode Anime. Taking lemons and making lemonade, they turned the series into a straight-up harem comedy that focuses on Takeya and Ren, which works pretty well in the allotted space.
The anime of Death Note has a bit of this. While nothing too important to the story is omitted, several bits of information that would help explain things a bit better are retained in the manga. This causes a problem in that the manga feels comparatively wordy, while the anime comes across as an abridged series, what with the way characters derive information from seemingly nowhere. For example, when Near detects that Mikami is X-Kira, the manga lays out his entire thought process. The anime makes it seem like he just made a lucky guess.
In Demon Slayer: Kimetsu no Yaiba, the anime changed how a few events unfolded in the story, compared to how it originally went in the manga:
The Full Focus Breathing training: in the manga, Tanjiro actually completed the whole training first by himself in 10 days, to only then show Zenitsu and Inosuke feeling worried that they’ve been left behind by Tanjiro’s progress, that’s where the two are coerced and taught by Shinobu on how to progress after Tanjiro’s failed attempts to explain to the boys how he did it before, Zenitsu and Inosuke then finish their training in 9 days. The anime made it so Tanjiro only progressed halfway through the training first, to then have Shinobu motivate Zenitsu and Inosuke to catch up, the final step of the training is completed by Tanjiro, Zenitsu and Inosuke at the same time. The anime staff likely wanted the main trio to feel relatively close in their power progress.
The segue into the Infinite Train arc: in the manga, after the boys had fully healed in the Butterfly Estate and completed their Full Focus Breathing training, Tanjiro acted overly polite as always by forcefully excusing Zenitsu, Inosuke and himself out of the the Butterfly Estate because they were all good and ready for fighting again, not wanting to waste time and resources by just lazing around 'til they were officially assigned into a mission. It’s only by coincidence that they get the mission to board the Infinite Train right away. The anime has Tanjiro be directly guided toward the Infinite Train mission, properly scheduled to start after his recovery in the Butterfly Estate. The anime staff likely wanted Tanjiro to be better placed into the Infinite Train build up.
When the anime was made, the manga was still ongoing. It turned what content was already written into different show parodies, and wrote its own ending based on what original content they made themselves.
The Latin-American dub toned down Excel's genki nature a little bit for practical reasons. She screams so much that in the English dub, Jessica Calvello ended up destroying her vocal cords (don't worry, she got better).
The 2006 anime: There was no way for a 24-episode television series to adapt the entire visual novel with its three alternate timelines and still tell a coherent story – so the anime mainly adapts the "Fate" route, which comes first. But it also adds in scenes and events from the "Unlimited Blade Works" route, to better feature characters who spend the "Fate" route Out of Focus and to hint at plot developments elaborated on in the second and third routes. They also threw in references to the "Heaven's Feel" route – namely, the revelation that Rin and Sakura are sisters.
The "Unlimited Blade Works" film: Especially noticeable. Some of the romantic undertones between Shirou and Rin are lost, and separate visits to locations in the original get merged into a single, very eventful one wherein things happen for different (but more easily explainable) reasons.
The first major manga: Like the original 2006 anime it follows the "Fate" route, but takes more material from "Unlimited Blade Works" specifically that after defeating Rider, Caster attacks the Emiya residence and steals the weakened Saber away with Rule Breaker, with events then playing out similarly to that route and including Archer's betrayal, Lancer teaming up with the heroes, and Archer betraying Caster and 'almost' killing Shirou. However, Saber doesn't make a contract with Rin and Rin reestablishes the pact between Shirou and Saber and between herself and Archer. It also throws in a few references to "Heaven's Feel", namely the reveal that Sakura is adopted into the Matous and is Rider's true Master.
FLCL: The manga adaptation isn't so much a retelling of the story in the anime as it is taking the same premise and characters and telling a completely different story.
Junji Ito did a manga adaptation of Frankenstein that patched a rather significant plot hole in the original work that would have been only more glaring to modern audiences. In the original story, Victor Frankenstein is threatened by the monster into creating a bride for him, but despite having everything on the line, he decides to destroy it before completion on the biologically nonsensical premise that the pair could spawn a whole race of similar monsters. In the manga, Victor goes through with it, since to do otherwise is to put himself and those he loves at risk. In the end, though, the bride ends up a mindless, violent monster rather than the thinking being his first creation was. The monster assumes Victor deliberately sabotaged the work and seeks his revenge. The manga also makes Henry Clerval into an Ascended Extra and because of his involvement with the female wretch, gives the monster a much more clear reason (to the audience) to kill him.
Fullmetal Alchemist (2003) was put into production when only a few volumes of the manga had been released, and the writers had to not only come up with a conclusion based on the existing material, but make a story that would span about 50 episodes. So, in addition to expanding on certain scenes from the manga and adapting everything they possibly could (namely light novel spinoffs and omake gags), the anime also gives most of the characters wildly different characterizations and the plot goes in a very different direction, complete with Gecko Ending. Creator Hiromu Arakawa even encouraged them to do this. In addition, the tone became much less optimistic, and the focus shifted toward themes like sacrifice and the value of life. The result was an anime that was widely praised by critics, but is very different from its source. Whether or not it's as good as (or better than) the manga is subject to much debate.
The anime of Goblin Slayer is pretty faithful to the original novels' A-plot, but delays the battle at Cow Girl's farm (the climax of volume 1) until after the arc at the Sword Maiden's city (volume 2), which helps make the Adventure Guild's willingness to help Goblin Slayer a much bigger payoff for all his hard and formerly thankless work. It also cuts the maneuverings of the gods, which don't add much more than color commentary.
The Grenadier anime, Grenadier ~The Smiling Senshi~, follows a Broad Strokes account of the manga, but without the After the End connotations of the later volumes of the manga, the last four members of the Juttensen, and the Iron-Masked Baron's final assault on the Capital.
The Haruhi SuzumiyaLight Novels' narration are one of the things that people like most about them. Unreliable Narrator Kyon tells us the story in a unique way, but adding the visual media to it destroys this, since you aren't told what happens anymore. Kyon does not have quotation marks when he talks, so it is ambiguous if he's talking or narrating. You can assume he is narrating for the most part, but sometimes character will reply to his supposed narration, much to the surprise of the reader. The anime actually manages to keep this by changing the camera perspective away from Kyon's mouth, so you don't actually see if he is narrating or talking.
By necessity, the anime adaptation of Hakuouki cannot cover all of the game's various divergent story paths. The anime thus primarily follows Hijikata's route, due to that route covering the most of the Shinsengumi's history, and incorporates significant scenes from other paths where they can fit into the sequence of events. The anime also adds scenes to provide closure for Okita and Harada's character arcs, since they separete from the Shinsengumi halfway through the storyline and disappear from Hijikata's route in the game.
Many, many things were shortened or outright removed in the Higurashi: When They Cry anime. The manga mostly averts this by leaving in most of the details, but the story is still compressed for time (the arcs are two volumes long).
JoJo's Bizarre Adventure: Diamond is Unbreakable: Four of the penultimate arcs ("Let's Live on a Transmission Tower", "Enigma Boy", "My Dad is not my Dad", and "Cheap Trick") were all covered separately, through flashbacks. For the 2016 adaptation, these events are, while still mostly linearly, shown happening when the events of said arcs started before covering those episodes, which neatly keeps the plot moving and streamlines what would otherwise likely be a confusing arc.
Kanamemo uses this to amplify the comedy, but also adds tons of Character Development for Kana, making her whole orphan situation much more realistic than in the manga. Backstory was added on the Fuushin Gazette by adding a new character that was never in the manga.
The Lyrical Nanoha movies each condense a 12-Episode Anime into a single movie, so naturally many things get cut, removing a lot of Worldbuilding and explanations of magic, as well as reducing the relative screen time of most characters or excising them entirely (in particular: Nanoha's family don't even get a single line, Yuuno gets Demoted to Extra from the beginning, and Graham isn't present at all). But what is left behind is expanded on: the relationships between Nanoha, Fate and Hayate are given more focus than in the series, and Precia and Reinforce are given extra backstory and character focus. The end result is something that's a bit difficult to understand for those unfamiliar with the series, but which, to fans, is exactly what they wanted.
Several things were toned down in the anime of Mazinger Z. In the original story, Dr. Kabuto was another Mad Scientist with his face scarred who had never met Dr. Hell. In the anime, he was a well-meaning nice old man who shared a backstory with Hell and built Mazinger Z for defending the world (apparently this was later retconned into manga continuity, since in the Great Mazinger manga Kouji claimed Dr. Hell had killed his grandfather). However, Kouji was nicer and less sexist — albeit a bigger pervert. Many manga characters (such like Inspector Ankokuji, the twin sisters Loru and Lori, or the Gamia assassin androids) and storylines never showed up in the anime. That, or their story was altered (such as Lorelei's story). Likewise, the anime came up with new characters (Professor Gordon and his daughter who modified Mazinger Z to be able to swim, or Viscount Pygman and Archduke Gorgon) developed some situations (Mazinger getting its Mid-Season Upgrade and other minor upgrades, the birth of Boss Borot) and characters (the other scientists of the Institute, Kouji and Sayaka's families) in a greater depth than the manga.
Miraculous: Tales of Ladybug & Cat Noir: Although the 2021 manga faithfully adapts the original cartoon's version of Stormy Weather and is mostly faithful to The Bubbler, the first Evillustrator chapter onwards integrates important plot details that were only revealed in Season 2. The manga also adds original content that wasn't in the TV episodes such as Adrien grieving over his mother and Marinette, in addition to Gabriel, having suspicions about his identity in order to move the plot along at a faster pace than the show. The Dark Cupid adaptation even includes an Adaptational Early Appearance from Luka.
Trading is a major element of the games — however, trading in the anime (and most other adaptations) is extremely rare. The individual Pokémon are treated as characters. Replacing them often wouldn't work as easily as in the games.
This trope is often a general aspect that occurs on a daily basis in the anime by really changing plot points in the games for more "child-friendly" versions to accommodate the plot. The Team Flare plot goes off-the-rails by importing a "Legendary Giant Rock"note An accurate, but unfortunately hilarious, translation of the original "Megalith" all the way from Hoenn, while in the original there was no such connection between Hoenn and Kalos. This was done to avoid showing on the big screen how the Ultimate Weapon was essentially a nuke powered up by living organisms that would leave them dead.
A more mundane example is how battles are conducted. The main Pokémon RPGs use Turn-Based Combat that wouldn't work well in a setting where Pokemon can move freely at any time. Other liberties are taken where elemental moves can cancel other moves and dodging is a legitimate option. As a result, Pokemon battles behave a bit more like Super Smash Bros. or Pokkén Tournament than the main RPGs. Also, Pokémon have Physical and Special Attack stats that dictate what moves they use, especially after the Physical-Special Split in Generation IV. This doesn't exist in the anime for obvious reasons, so this leads to things like Sawyer's Clawitzer using Aqua Jet and Crabhammer which are Physical moves even though its stats indicate it only uses Special Moves.
The Gyms are depicted as battlefields because it would be too hard to incorporate the puzzles to reach the Gym Leader in the games such as Snowpoint Gym's (which requires the player to climb up to higher ledges and slide down to smash snowballs in the middle of the gym) and Humilau Gym's (which requires the player to ride lily pads to wooden platforms to reach Marlon).
The Promised Neverland uses a lot of inner monologues to showcase the characters' thinking process during their intellectual battles and the Xanatos Speed Chess between them, as well as a lot of Imagine Spots to highlight the thoughts or the fears of the characters. The anime eliminates all narration and inner monologues, occasionally integrating some of it in the spoken dialogue, and also removes the Imagine Spots. As a result, the show has a faster pace and a more down-to-earth atmosphere, but focuses more on visual, auditive and emotional tension, and slightly less on the intellectual and psychological aspects of the conflict. Also, instead of inventing a unpronounceable name for the Demons' supreme god, the anime only refers to it as "that Person" to preserve its aura of mystery. The English dub refers to him as "the One".
Persona -trinity soul- was supposed to take place in the same universe as Persona 3 (at least, the presence of Akihiko implies that much), though the anime has since been declared non-canon. However, the rules for Persona summoning are drastically changed for pragmatic reasons. In the games, a Persona has to be repeatedly summoned for every skill you use. This works wonderfully for a turned based game, but it would lack the same effect in an animated series. So in Trinity Soul, the "rules" for Personas were changed so that the battles would look more visually engaging.
The manga adaptations of Persona 3 and Persona 4 modified the rules for Persona users quite a bit. For example, Mitsuru at one point was seen using Persona powers to freeze the cast outside the Dark Hour, which was eventually revealed to be possible, but the cast wasn't capable of it at this point, only learning to do it years later.
Persona 4: The Animation condenses a 90+ hour game into 26 half-hour episodes, showing no class time and cutting out the vast majority of the dungeon crawling—basically showing condensed versions of the dungeon plots and then skipping straight to the boss battles. (However, they also show the very sidestory-ish Social Link plots.) Similarly, the team no longer uses weapons, since it's a whole lot harder to convince viewers that the investigation team has been sneaking swords and chairs into Junes under their clothes when everything is being fully animated.
The same can be said for Persona 3: The Movie, with the Social Links only appeared as cameos (with the exceptions of two, albeit altered and one of them is from female MC in Portable) and the story focuses entirely on the SEES and its main plot, therefore resulting in Makoto gaining a new arcana for his Wild Card after each Full Moon operation. In contrast to the above series, the team fights using their weapons, although they were manufactured by the company instead of the police officer, and Makoto goes on Portable route where he’s limited to just shortsword.
The Persona 4 manga adaptation takes some liberties with the Social Links. Yosuke, rather than Soji, is the one who befriends Naoki and helps him come to terms with his older sister Saki's passing(Saki happens to be the girl Yosuke had a crush on), resulting in Yosuke's Persona evolving. In the manga, Adachi's Social Link takes place just after Dojima and Nanako are hospitalized, resulting in Soji being alone at the Dojima residence, even though the event in question is the deadline to get to Rank 6 of Adachi's Social Link, and the other ranks come in story events.
In Ranking of Kings, the anime is following the manga's story progression faithfully but it shuffles the order in which some deeper character motivations are unveiled, raising the tension for anime viewers, making them wait a little while for what certain characters are really about.
Rebuild of Evangelion cuts lots of things that appeared in the show in order to save time. Most significantly, Ritsuko is almost Demoted to Extra, and a number of the Angels were also excluded while others were turned into Composite Characters. No longer applies as of 3.0, however, due to going seriously Off the Rails.
Haruka and Michiru's lesbian relationship is glossed over in many dubs, such as The '90s Cloverway North American dub, which infamously changed them to cousins. Amusingly, the dub seemed primarily concerned with modifying only the most blatant comments. The two are still unusually affectionate, if not outright romantic.
The anime version of School-Live! had to change numerous things in order to fit in Taroumaru, who originally was an Oneshot Character. The ending episode was changed considerably. No mention of the rescue helicopter is made and thus there's no scene with it crashing and blowing up. The Tear Jerker is instead how Taroumaru doesn't make it even with the anti-zombie vaccine. The episode ends on a considerably lighter turn due to Miki and Kurumi lacking injuries, Yuuri never having her breakdown, and Yuki never killing a zombie and her world subsequently crashing down on her, though it still has a Bittersweet Ending.
Sound! Euphonium is light on this for an adaptation of a light novel, but a noticeable example comes from a pivotal scene near the middle of the first arc. Wanting to stand out from other marching bands at a festival, the protagonists' band director chooses an unorthodox pop song for their performance. In the novel, it's "Can't Buy Me Love" by The Beatles, while in the anime, it's "Rydeen" by Yellow Magic Orchestra. Both songs show the director's unusual taste in music for his profession, but an uptempo rock tune like "Can't Buy Me Love" would be difficult to adapt to the marching band format. "Rydeen", which was likely chosen due to the legal difficulty of licensing a Beatles song, has the added bonus of being easier to adapt to begin with; it already has a marching rhythm and steady tempo. As an extra layer of boldness, "Rydeen" being a Japanese pop song sticks out more here, since most traditional marching band songs are Western compositions.
In the Splatoon games, players cannot battle those that are outside of their rank range. Usually players will battle only those in their rank, though matchmaking may allow one to battle players one level above/below them unless they are in the S+ or X ranges. The manga completely disregards this to have Blue Team made up of a C-, a C, a C+, and a B-, and allowing them to battle Inklings who are S and above.
In the games, unless it's a Splatfest or one has "Color Lock" enabled, Inklings change colours for every match. In the manga, characters are organized by colour and always stay that colour.
The first Hero Mode arc features both Goggles and Rider acting as Agent 3, even though this role was filled by a single character during the first game. By the time of the Octo Expansion arc, this is dealt with by having Goggles be an "agent" (in the Secret Agent sense) with the rest of Blue Team, while Rider gets Agent 3's in-game appearance.
When the original Space Battleship Yamato was created, it was generally assumed that the WWII Battleship Yamato sunk and remained in one piece. In 1985, it was discovered that this was not the case. The 2010 2199 remake couldn't plausibly justify the idea of building a spaceship out of the wreck of the Yamato. Therefore, the sunken wreck was turned into camouflage for a completely new ship that was being built under it.
The manga adaptation of the first Tenchi Muyo! movie, Tenchi Muyo in Love, changes a lot of the second half of the movie — the Galaxy Police agent seeking him is excised completely, a mistake on Mihoshi's part is added in (the manga has Mihoshi mess up and go to the wrong shrine needed to set up a special dimension portal) and the final battle is condensed and changed (Achika sees Tenchi's final fight with Kagato instead of the lonely, crying young Tenchi and Tenchi fights Kain with Achika using her powers to help deliver the final blow instead of Achika fighting him solo).
Tokyo Ghoul condenses approximately 80 chapters worth of material into a 12-episode anime, with break-neck pacing and many scenes removed for the sake of brevity. It also switches the order of the arcs focusing on Hinami and the Ghoul Restaurant, allowing the characters killed in the first arc to live longer in the anime and introducing Tsukiyama earlier.
The Virtua Fighter anime turns Akira from being more or less a Ryu clone into a Big EaterIdiot Hero more akin to Goku; also, it turns Pai into a Tsundere that's heavy on the Tsun, Jacky into a Deadpan Snarker, and Sarah into a Girly Girl with a flying squirrel, at least until she's brainwashed. The anime also eschews the World Fighting Tournament from the games, focusing on the heroes fighting against huge criminal organizations. The anime retains other elements, such as Sarah's kidnapping and brainwashing, Pai's estranged relationship with her father Lau, and the creation of Dural. The main plot itself involves Pai trying to avoid being kidnapped and married to the villain, which her father had arranged so there would be a successor to the fighting style of Koenkan. Said villain has turned it into a criminal organization, something that was never in the games. Since the games themselves are very light on plot and characterization, there wasn't much to mess up.
The anime adaptation of The World God Only Knows is extremely faithful to the manga, but about the biggest change is that the second-to-last episode of the second season was chapter 41 of the manga; then, for the finale, chapter 75 was adapted. The reason this worked was because chapter 75 contained none of the new characters that had been introduced in the interim in the manga, so nothing was spoiled. Then the third season jumps ahead to the Goddess arc, effectively skipping over 50 chapters of, admittedly, highly repetitive story.
The anime adaption of Yo-kai Watch, in order to distinguish itself from other Mons anime, focused on using summoned Yo-Kai's abilities to change emotions and behavior to defeat the section's yokai, rather then direct battles. This is different to the video games the anime is based on, where Yo-Kai do directly battle each other.
The Yu-Gi-Oh! anime's adaptation of the manga's Millennium World arc. The very complex tabletop RPG was simplified, and Seto's battle with the Pharaoh took place just before Zorc awoke rather than after his defeat. In exchange, Kisara and Yugi's friends got more to do, and the consequences of Yugi's wish for friends was brought up as well.
